Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $61.74   8.629%   $67.0675   $67.07   $67.05   $67.10  
  Purchase #2 $212.84   3.779%   $220.8832   $220.88   $220.90   $220.90  
  Purchase #3 $92.45   11.357%   $102.9495   $102.95   $102.95   $102.90  
  Purchase #4 $172.66   6.277%   $183.4979   $183.50   $183.50   $183.50  
  Purchase #5 $244.28   9.850%   $268.3416   $268.34   $268.35   $268.30  
  Purchase #6 $97.67   8.353%   $105.8284   $105.83   $105.85   $105.80  
  Purchase #7 $172.73   6.203%   $183.4444   $183.44   $183.45   $183.40  
  7 purchase totals = $1,054.37       $1,132.0125   $1,132.01   $1,132.05   $1,131.90